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Physics

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Tuesday 23 June

High Energy Physics (Phenomenology)

The $a_1(1420)$ in a Unitary Coupled-Channel Three-Body Approach

Ajay S. Sakthivasan, Yuchuan Feng, Michael Döring et al. (+1 more)

An enhancement in the three-pion energy at around $\sqrt{s}\approx 1.42~\textrm{GeV}$ with $a_1$ quantum numbers was observed at the COMPASS experiment. This was later attributed to the triangle singularity mechanism involving an on-shell $K^*(892)$, $K$ and $\bar K$ intermediate states. The alignment of the decay $K$ with the spectator $\bar K$ produces an $f_0(980)$, resulting in a kinematic enhancement, which is classically explained by the Landau equations. However, this one-loop process forms only part of a non-diagonal transition in a much larger coupled-channel framework. This study demonstrates the feasibility of embedding one-loop triangle-singularity calculations into a unitary three-body amplitude allowing one to consistently incorporate final-state interactions and their potentially substantial effect. For this, up to $P$-wave isobars and all sub-channel isospins are combined in a nine-channel production amplitude that is fitted to COMPASS lineshapes at different momentum transfers. The fitted amplitude reproduces the narrow enhancement in the $(\pi f_0)_P$ channel near $\sqrt{s}\approx1.42$ GeV. This implies that the triangle singularity mechanism sufficiently explains the observed enhancement, and an additional genuine $a_1(1420)$ pole is not required. Incidentally, the parameters of the ground state axial vector resonance (the $a_1(1260)$) are also extracted from that data.
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All authors Ajay S. Sakthivasan, Yuchuan Feng, Michael Döring, Maxim Mai

High Energy Physics (Theory) · Cross-listed from math.QA

Vertex Superalgebras for Hypertoric Varieties and 3d Abelian Gauge Theories

Tomoyuki Arakawa, Andrea E. V. Ferrari and Sven Möller

Hypertoric (or toric hyperkähler) varieties are a class of symplectic singularities and their resolutions, obtained as Hamiltonian reductions of a symplectic vector space acted on by a torus. In physics, they appear as Higgs (and Coulomb) branches of 3d $\mathcal{N}=4$ supersymmetric quantum field theories with abelian gauge group. In this work, we construct an $\hbar$-adic (in the sense of microlocalisation) sheaf of vertex operator superalgebras over a given smooth hypertoric variety. Its global sections give the $A$-twisted boundary of the corresponding 3d gauge theory. We use this to prove that the associated affine variety of this hypertoric vertex operator superalgebra recovers the singular hypertoric variety. This proves the 3d Higgs branch conjecture for a large class of boundary vertex operator superalgebras. In particular, these vertex operator superalgebras are quasi-lisse. This is in contrast to the (purely even) hypertoric vertex operator superalgebras (and their $\hbar$-adic localisations) constructed previously by Kuwabara as global sections of sheaves on families of universal Poisson deformations of the hypertoric varieties. These are generally not quasi-lisse. We show that the vertex operator superalgebras defined in this paper are (fermionic) simple-current extensions of those defined by Kuwabara, and investigate the consequences for symplectic duality and characters. We observe that the latter are upgraded from partial (or false) theta functions to quasimodular forms.
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Astrophysics of Galaxies

Traversing the Galactic Centre in space and time

Michal Zajaček, Bożena Czerny, Martin Mondek et al. (+5 more)

The Galactic Center is often identified with its central supermassive black hole, Sgr A*. Yet the black hole governs gravitationally only the innermost few parsecs of the Milky Way, while the surrounding Nuclear Star Cluster, Nuclear Stellar Disc and Central Molecular Zone (CMZ) shape the dynamics of stars and gas on progressively larger scales. Understanding how these components interact is essential not only for reconstructing the history of our own Galaxy, but also for interpreting galactic nuclei more generally.
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All authors Michal Zajaček, Bożena Czerny, Martin Mondek, Samik Mitra, Matúš Labaj, Tomáš Ondro, Jan Janík, Jiří Dušek

Quantum Physics

Tuning topological phases and exceptional points in a non-Hermitian Rice Mele model beyond nearest neighbors

Carolina Martinez-Strasser, Dario Bercioux and Nico Leumer

Exceptional points are degeneracies characteristic of non-Hermitian operators, where eigenvalues and eigenvectors coalesce, rendering the Hamiltonian defective. We investigate the exceptional-point structure and topological properties of a generalized non-Hermitian Rice-Mele model with balanced gain and loss, as well as next-nearest-neighbor hopping. The system hosts only second-order exceptional points under both periodic and open boundary conditions. Under periodic boundary conditions, the exceptional points in parameter space lie on lines and ellipses that are independent of the next-nearest-neighbor hopping, since the latter enters the bulk Hamiltonian only as an identity contribution. Under open boundary conditions, this independence is broken: the next-nearest-neighbor hopping not only shifts the energy of existing exceptional points but also generates new ones, with a specific condition signaling a topological gap closing observed only in the open-boundary spectrum. At special parameter points, multiple simultaneous second-order exceptional points yield degenerate configurations whose degeneracy grows with system size. Exceptional point locations are identified numerically via the condition number of the eigenvector matrix and confirmed by Jordan decomposition. The topological phase diagram, computed via a winding number framework for non-Hermitian systems without symmetry protection, reveals sectors with zero, one, and two edge states; the bulk-boundary correspondence is confirmed, and the non-Hermitian skin effect is absent.
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Mathematical Physics · Cross-listed from math.AP

The sine Gordon equation in light-cone coordinates on the half lines revisited: a Riemann–Hilbert approach

Iryna Karpenko

In this work, we study the initial boundary value (IBV) problems for the sine-Gordon (sG) equation in the light-cone coordinates $u_{xt}=\sin u$ in the quarter planes $x> 0$, $t>0$ and $x< 0$, $t>0$ assuming a suitable decay as $x\to +\infty$ or as $x\to -\infty$. Employing the Riemann–Hilbert (RH) problem framework, we demonstrate that these two IBV problems differ significantly with respect to the boundary data required for well-posedness. Specifically, the solution of the “right problem” ($x\ge 0$) is uniquely determined by the initial data $u(x,0)$, $x\ge 0$ alone whereas for the “left problem” ($x\le 0$), the boundary data $u(0,t)$ has to be prescribed in addition to the initial data in order to obtain a well-posed problem.
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High Energy Physics (Phenomenology)

Reweighting Underlying Event and Colour Reconnection parameter variations in Sherpa

Moritz Pabst, Max Knobbe, Frank Krauss et al. (+1 more)

We propose and validate a new method to trace the impact of parameter variations in the simulation of multi-parton interactions and colour reconnections in the Sherpa event generator. They are reflected, at an event-by-event basis, through relative weights with respect to the central production parameters that give rise to the generated events and distributions. Our method facilitates the tuning of the Monte Carlo event generator at a dramatically reduced computational cost, alleviates parameter sensitivity studies, and enables robust quantification of parametric uncertainties on-the-fly, one of the missing ingredients for future simulations of high-energy particle collisions. The method can easily be adapted to and implemented in other event generators. To illustrate its potential, we here consider combined tunes of the multi-parton-interaction and colour-reconnection models in Sherpa using LHC proton-proton collision data at $\sqrt{s}=7\,\text{TeV}$. We furthermore calibrate the energy-scaling behaviour of dimensionful model parameters based on $\sqrt{s}=13\,\text{TeV}$ LHC data and Tevatron data taken at $\sqrt{s}=1.96\,\text{TeV}$.
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All authors Moritz Pabst, Max Knobbe, Frank Krauss, Steffen Schumann

High Energy Physics (Phenomenology)

Second-order effective renormalized Hamiltonian of Quantum Chromodynamics

Kamil Serafin, Carter M. Gustin and Peter J. Love

The effective Hamiltonian of quantum chromodynamics in the front form of Hamiltonian dynamics is calculated and renormalized. The renormalization group procedure for effective particles up to the second order in the coupling constant is used. Small gluon mass is used to regulate infrared singularities of the theory. The counterterms necessary to renormalize the theory are determined by computing matrix elements of the effective Hamiltonian. The effective Hamiltonians are well-defined symmetric forms on a dense subspace of the Fock space. The zero modes are cut off but, once ultraviolet renormalization is performed, no divergences are found in the color singlet subspace in the limit of the gluon mass approaching zero. A major result is that the interplay between self-energy terms and gluon exchange effective terms generates a term proportional to the quadratic SU(3) Casimir operator times the logarithm of the gluon mass. Therefore, the matrix elements are logarithmically divergent in the color nonsinglet subspace, but finite in the color singlet subspace, because the Casimir operator vanishes in the color singlet subspace. The effective Hamiltonians are suitable for nonperturbative numerical calculations using either classical or quantum computers.
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General Relativity and Quantum Cosmology

Reduction of the Finsler gravity vacuum equation and dynamics for the cosmological Landsberg spacetimes

Christian Pfeifer and Fidel F. Villaseñor

When solving the Einstein vacuum equations, a very helpful feature is that they reduce simply to the vanishing of the Ricci tensor. In Finsler gravity, a promising extension of general relativity that can describe the gravitational field of kinetic gases from a phase space perspective in terms of Finsler geometry, such a reduction is not as straightforward. In this article, we identify precise conditions under which the scalar Finsler gravity vacuum equation (in either its purely metric or its Palatini formulation) reduces to the vanishing of the Finslerian Ricci curvature. Through analytic arguments, we find that this happens if there exists some power $F^n$ of the Finsler function $F$ that is sufficiently regular and whose associated Finsler metric is non-degenerate on the light cones. Moreover, the Landsberg term in the scalar equation must vanish. This result significantly generalizes the findings of [Villasenor2024], where a reduction theorem was established under the quite strong assumption that $F^2$ is regular, which is not satisfied by many examples currently under consideration. We demonstrate the impact of our findings by applying them to solve the Finsler gravity equations for homogeneous and isotropic Finsler spacetime functions of Landsberg type.
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Cosmology and Nongalactic Astrophysics

Euclid preparation. First investigation of the impact of cross-contamination on spectroscopic redshift measurements with pixel-level simulations

Euclid Collaboration: F. Passalacqua, S. Anselmi, P. Monaco et al. (+298 more)

We present a study on simulated data focused on understanding the performance of the spectroscopic redshift measurements with the Near-Infrared Spectrometer and Photometer (NISP) instrument on Euclid. Simulations include scenarios with different levels of cross-contamination arising from overlapping spectra of nearby sources, which represents one of the main drawbacks of slitless spectroscopy. We present a new analysis based on pixel-level simulations of the NISP images, with the data processed using the Euclid spectroscopic pipeline. We first consider an idealised case with non-overlapping spectra to assess the accuracy and reliability of the redshift measurement as a function of the flux of the H-alpha emission line and galaxy size. We then introduce more realistic contamination scenarios, distinguishing between two contributions: contamination from H-alpha emitters, which are the Euclid targets for cosmological analyses, and contamination from all other galaxies. In the second case, we analyse the impact of cross-contamination with an increasing number of contaminants, from the brighter to the fainter galaxies. Given that our results show no clear evidence that sources fainter than magnitude 20 degrade redshift measurements, we conservatively restrict our analysis to galaxies with magnitudes up to 24. In particular, we provide a preliminary estimate that contamination from galaxies within the same redshift range as the target sample contributes to about 4% of the total degradation due to cross-contamination from all galaxies.
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All authors Euclid Collaboration: F. Passalacqua, S. Anselmi, P. Monaco, C. Sirignano, S. Dusini, N. Fourmanoit, M. Fumana, E. Lecrivain, K. S. McCarthy, M. Moresco, F. Oppizzi, A. Renzi, M. Scodeggio, L. Stanco, A. Troja, S. Bruton, C. Carbone, S. de la Torre, B. R. Granett, G. Lavaux, S. Lee, K. Markovic, W. J. Percival, I. Risso, C. Scarlata, E. Sefusatti, Y. Wang, S. Andreon, N. Auricchio, H. Aussel, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, E. Branchini, M. Brescia, S. Camera, G. Cañas-Herrera, V. Capobianco, V. F. Cardone, J. Carretero, S. Casas, F. J. Castander, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, C. A. J. Duncan, X. Dupac, S. Escoffier, M. Farina, S. Ferriol, S. Fotopoulou, M. Frailis, E. Franceschi, L. Gabarra, S. Galeotta, K. George, W. Gillard, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, L. Guzzo, W. G. Hartley, S. V. H. Haugan, S. Hemmati, W. Holmes, F. Hormuth, A. Hornstrup, P. Hudelot, K. Jahnke, M. Jhabvala, B. Joachimi, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, V. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, M. Magliocchetti, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, N. Mauri, C. J. R. McPartland, E. Medinaceli, S. Mei, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, C. Moretti, L. Moscardini, E. Munari, R. Nakajima, C. Neissner, R. C. Nichol, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, G. D. Racca, F. Raison, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, C. Rosset, E. Rossetti, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, G. Seidel, S. Serrano, P. Simon, G. Sirri, J. Steinwagner, C. Surace, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, D. Vibert, J. Weller, G. Zamorani, E. Zucca, V. Allevato, M. Ballardini, A. Boucaud, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, J. A. Escartin Vigo, R. Maoli, J. Martín-Fleitas, S. Matthew, R. B. Metcalf, M. Pöntinen, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, M. Archidiacono, F. Atrio-Barandela, P. Bergamini, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, M. Bonici, S. Borgani, M. L. Brown, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, A. R. Cooray, O. Cucciati, S. Davini, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, M. Y. Elkhashab, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Fontana, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, S. Joudaki, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, A. Loureiro, J. Macias-Perez, C. Mancini, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, G. Morgante, S. Nadathur, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, D. Paoletti, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, G. Rodighiero, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, M. Tucci, D. Vergani, G. Verza, P. Vielzeuf, N. A. Walton

Fluid Dynamics

A Physics-Informed Fourier-Wavelet Transformer for Multiscale Computational Fluid Dynamics Surrogate Modeling

Somyajit Chakraborty, Ming Pan and Xizhong Chen

Physics-informed surrogate models can accelerate computational fluid dynamics simulations. However, many existing methods reproduce global flow patterns more reliably than localized multiscale structures. This study presents a physics-informed Fourier-wavelet transformer for next-step velocity-field reconstruction in real-world flow benchmarks. The proposed formulation combines hybrid Fourier-wavelet spectral encoding with physics-biased self-attention based on partial differential equation residual diagnostics. It also uses self-supervised pretraining through Masked Physics Prediction and Equation Consistency Prediction. The experiments are conducted on two real benchmark cases: cylinder-wake flow and fluid-structure interaction. All approaches are evaluated under a shared local protocol and compared with spectral, transformer-based, operator-learning, and physics-informed neural-network baselines. On the cylinder-wake benchmark, the proposed model achieves the best aggregate accuracy, with an all-channel normalized mean-squared error of 0.05875 and an all-channel Pearson correlation coefficient of 0.97019. On the fluid-structure-interaction benchmark, it gives the lowest all-channel normalized mean-squared error of $2.70 \times 10^{-4}$, compared with $4.02 \times 10^{-4}$ for the strongest baseline. Component-wise field comparisons and scale-separated diagnostics further show stronger recovery of localized wake structures, including near-body, wake-core, and far-wake features. The results demonstrate improved real-world flow reconstruction while maintaining a practical accuracy-cost tradeoff.
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Optics

Widely tunable optical parametric oscillation and visible light generation in 4H-SiC microresonators

Yongsheng Wang, Shuangyou Zhang, Yurong Ren et al. (+3 more)

Widely separated optical parametric oscillation (OPO) represents a powerful method for coherent wavelength conversion across infrared and visible spectra. While such generation has been demonstrated in material platforms like silicon nitride and lithium niobate, 4H-SiC remains unexplored despite offering combined strong second-order and third-order nonlinearities with ultralow material loss. Here we demonstrate tunable, widely separated OPO generation in 4H-SiC microresonators through dispersion engineering. By optimizing the resonator geometry to achieve normal dispersion at telecommunication wavelengths and pumping at around 1550 nm, a pair of signal and idler spanning nearly an octave is generated,which represents the first demonstration of widely separated OPO in 4H-SiC. The frequency separation is tuned by varying the pump wavelength, with measured signal and idler wavelengths align well with phase-matching prediction. Leveraging the non-centrosymmetric crystal structure of 4HSiC, the generated OPO signal undergoes cascaded second-harmonic generation (SHG) and sum-frequency generation (SFG) with the pump, yielding coherent visible light at wavelengths below 700 nm. This cascaded upconversion of widely separated OPO signals represents a novel pathway for visible light generation. These results establish 4H-SiC as a promising platform for nonlinear wavelength conversion spanning from visible to 2 um region.
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All authors Yongsheng Wang, Shuangyou Zhang, Yurong Ren, Paolo Leonelli, Mingjun Chi, Haiyan Ou

Space Physics

The Billion Dollar Surprise: How Solar Cycle 25 Cut Satellite Lifetimes in LEO

Scott Shambaugh

Solar Cycle 25 has run far stronger than the 2019 consensus forecast issued by the NOAA/NASA/ISES prediction panel, with densities in low Earth orbit from 2022-2026 holding at 2-3x the predicted levels. The cumulative drag impulse experienced by LEO satellites reached 5-6 standard deviations beyond the forecast's stated uncertainty. This means that even operators who designed conservatively against the two-sigma worst case fell short of their drag budgets. This paper quantifies a lower bound on the economic cost of that misprediction. Starting from the 13,704 payloads on-orbit below 800 km during 2022-2026, we screen to the 1,597 payloads which we validated with high confidence to be both operational and in ballistic freefall. We estimate each satellite's ballistic coefficient and propagate its trajectory under the forecasted atmosphere versus the observed one. A probabilistic cost model assigns each satellite an annualized mission cost based on direct costs (amortized capital costs plus annual operations), stratified by size class, with bespoke estimates for high value missions. Survival and forward cost discounting is applied at a modal 11% per year. We combine the differences in lifetime with the cost model to estimate the total dollar impact. Against the forecast's two-sigma upper bound which we consider to be a standard engineering design target, these satellites lost 688 cumulative mission years valued at \$0.88 billion. Against the nominal forecast, they lost 2,472 mission years worth \$2.77 billion. These estimates are deliberate lower bounds which exclude propulsive satellites, revenue above direct cost, and downstream economic impact. The results give a quantitative case for the value of accurate decadal-scale space weather forecasting, and show that well-calibrated uncertainties are as valuable to a satellite operator end-user as the accuracy of the central prediction itself.
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Astrophysics of Galaxies

Only obscured yet luminous active galactic nuclei are closely associated with galaxy mergers: Direct observational evidence from type 2 active galactic nuclei

Yongmin Yoon, Yongjung Kim, Dohyeong Kim et al. (+2 more)

To establish a more comprehensive understanding of the connection between galaxy mergers and active galactic nuclei (AGNs), it is essential to disentangle the contributions of intrinsic AGN luminosity and dust extinction to the merger-AGN connection. Since tidal features identified in deep images serve as direct evidence of recent mergers, we studied the fraction of AGN hosts with tidal features ($f_T$) for a large sample of 748 type 2 AGNs at $z<0.063$. Specifically, we examined $f_T$ as a function of $E(B-V)$, derived from the Balmer decrement, and the internal-extinction-corrected luminosity of the [O III] $\lambda$5007 emission line ($L_{\text{[O III]}}$), which is a proxy for bolometric AGN luminosity. Our main finding is that $f_T$ is only significantly higher for AGNs that are simultaneously luminous and heavily dust-obscured. Specifically, AGNs with $\log L_{\text{[O III]}}\gtrsim41.5$ and $E(B-V)\gtrsim0.7$ exhibit a high $f_T$ of $\sim0.7$. In contrast, AGNs with either low luminosity ($\log L_{\text{[O III]}}\lesssim41.0$) or low dust obscuration ($E(B-V)\lesssim0.3$) show a low $f_T$ of $\lesssim0.2$. This trend suggests that galaxy mergers preferentially trigger AGNs that are simultaneously luminous and dust-obscured, whereas AGNs that are either luminous but unobscured or dust-obscured but less luminous are not strongly associated with merger-driven triggering. Based on several assumptions, our result can also be interpreted, despite certain caveats, within the framework of a merger-initiated evolution model for AGNs, suggesting that AGNs that are both obscured and luminous are temporally closer to merger events than those with lower luminosities and less dust obscuration.
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All authors Yongmin Yoon, Yongjung Kim, Dohyeong Kim, Jaejun Cho, Woowon Byun

Quantum Physics

A Universal Telecom-Band Quantum Memory Enabled by Cross-Phase Modulation

Domenico Compagnini, Noemi Tagliavacche, Sara Congia et al. (+4 more)

Quantum memories capable of storing and retrieving photonic quantum states on demand are essential for quantum communication, entanglement distribution, and the synchronization of probabilistic quantum processes. All-optical loop-based memories offer broadband operation and compatibility with telecommunication infrastructure, but their performance is often limited by switching losses and the noise introduced by active control mechanisms. Here, we demonstrate a universal all-fiber quantum memory based on two Sagnac interferometers acting as dynamically controlled mirrors through cross-phase modulation. This all-optical switching mechanism enables an input/output transmission as high as 90% (0.46 dB insertion loss), a round-trip transmission of 94.6%, and a characteristic storage lifetime of $18.54 \pm 0.21 \mu s$. The memory exhibits an operational spectral range exceeding 12.5 THz, while keeping noise to negligible levels across the whole telecom C-band. We experimentally demonstrate the preservation of time-bin-encoded heralded photons and time-bin entanglement, as well as compatibility with polarization- and frequency-bin-encoded optical states. Furthermore, we demonstrate the simultaneous storage of over 200 temporal modes and the selective retrieval of independently addressable modes. Our results establish low-noise switching as a promising approach to broadband quantum memories combining high transmission, encoding versatility, and programmable temporal-mode control.
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All authors Domenico Compagnini, Noemi Tagliavacche, Sara Congia, Andrea Bernardi, Marco Liscidini, Matteo Galli, Daniele Bajoni

Atomic Physics

Nonlinear refractive index of warm rubidium vapor

L. Kardum, G. Premec, N. Šantić et al. (+1 more)

The potential to precisely control both the linear and nonlinear index of refraction through optical manipulation of the atomic states has recently pushed warm alkali vapors to the forefront of research in the field of quantum sensors, quantum memories, and quantum fluids of light. Rubidium (Rb) vapor in centimeter-scale glass cells or millimeter-scale MEMS cells has proven to be a very promising platform for these applications, yet only a handful of research works have been dedicated to the investigation of the (non)linear refractive index of Rb vapor. We present results of theoretical calculations of the (non)linear refractive index of warm Rb vapor, based on the optical Bloch equations for 6-level Rb atoms interacting with a probe laser. They are compared to the experimental results obtained using an interferometric technique, showing excellent quantitative agreement. A Kerr nonlinear refractive index $n_2$ of up to $10^{-4}$ cm$^2$/W is obtained. Python scripts for all theoretical calculations presented in this work are provided, including the refractive index calculation, that can readily be used in practical implementations for simulating the (non)linear refractive index of Rb vapor including the effects of Doppler broadening, transit time broadening, pressure broadening, saturation, optical pumping, and spin-exchange collisions.
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All authors L. Kardum, G. Premec, N. Šantić, D. Aumiler

Soft Condensed Matter

Thermal stability of vapor-deposited stable glasses of an organic semiconductor

Diane M. Walters, Ranko Richert and M. D. Ediger

Vapor-deposited organic glasses can show enhanced kinetic stability relative to liquid-cooled glasses. When such stable glasses of model glassformers are annealed above the glass transition temperature Tg, they lose their thermal stability and transform into the supercooled liquid via constant velocity propagating fronts. In this work, we show that vapor-deposited glasses of an organic semiconductor, N,N-bis(3-methylphenyl)-N,N-diphenylbenzidine (TPD), also transform via propagating fronts. Using spectroscopic ellipsometry and a new high-throughput annealing protocol, we measure transformation front velocities for TPD glasses prepared with substrate temperatures (TSubstrate) from 0.63 to 0.96 Tg, at many different annealing temperatures. We observe that the front velocity varies by over an order of magnitude with TSubstrate, while the activation energy remains constant. Using dielectric spectroscopy, we measure the structural relaxation time of supercooled TPD. We find that the mobility of the liquid and the structure of the glass are independent factors in controlling the thermal stability of TPD films. In comparison to model glassformers, the transformation fronts of TPD have similar velocities and a similar dependence on TSubstrate, suggesting universal behavior. These results may aid in designing active layers in organic electronic devices with improved thermal stability.
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Materials Science

Fractional Magnonic Frequency Combs

Qian-Nan Huang, Zhiping Xue, Xudong Wang et al. (+5 more)

Magnonic frequency combs (MFCs) are spectacular phenomena in microwave-driven high-quality magnets. Like the equally spaced prongs in a comb, conventional integer MFCs are sharp resonances with an equal and constant frequency difference. Here we report fractional MFCs in a high-quality magnetic sphere that emerges when adding a low-power, precisely detuned microwave to the main drive that compresses the frequency spacings to a rational fraction of the original comb, generating high-density spectral grids with hundreds of lines. The theoretical analysis finds that parametric three-magnon scattering is the dominant non-linear process that reproduces the observation well. This mechanism is unique to magnets: it does not exist in an optomechanical system, where the Kerr and optical nonlinearities govern comb formation at a much higher power input. Since our platform operates as a frequency “vernier caliper" with much higher sensitivity than integer MFCs, it has application potential in precision metrology.
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All authors Qian-Nan Huang, Zhiping Xue, Xudong Wang, Yanmeng Lei, Lihui Bai, Ke Xia, Gerrit E. W. Bauer, Tao Yu

Disordered Systems and Neural Networks

Anderson localization on the Bethe lattice

Dafne Prado Bandeira, Angelica Vecchiarelli and Marco Tarzia

Anderson localization - the suppression of wave propagation by interference in a sufficiently disordered medium - is one of the most remarkable phenomena in condensed matter physics. These lecture notes provide a pedagogical introduction to Anderson localization on the Bethe lattice, an infinite tree with fixed connectivity and no loops, and one of the few settings in which the transition can be studied exactly. The problem is important for two main reasons. First, the Anderson model on the Bethe lattice provides a mean-field, infinite-dimensional limit in which the transition point and critical behavior can be determined exactly. Second, it provides a simplified description of the high-dimensional configuration spaces of interacting quantum systems, and thus a useful toy model for many-body localization. We focus on the Green's function formalism and the cavity method. After recalling standard diagnostics of localization based on transport, spectral statistics, and eigenfunction moments, we show that they are encoded in the statistics of the Green's functions, and that the full distribution of the local density of states is the natural order parameter of the transition. We derive the exact self-consistent cavity equations on the Bethe lattice, use them to characterize the two phases and critical behavior - including an analytic solution at large connectivity - and describe population-dynamics algorithms that solve them with high precision. We explain how an exponentially large correlation volume and the localized nature of the critical point account for the strong finite-size effects on random regular graphs, which led to a long debate over a possible intermediate non-ergodic phase. Finally, we discuss the mapping onto directed polymers in random media, interpreting localization as a freezing transition dominated by a few rare resonant paths.
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Mesoscale and Nanoscale Physics

Simulating the Haldane model in ultra-clean GaAs heterostructures

Francesco Cioni, Lorenzo Cavicchi, Fabio Taddei et al. (+1 more)

The Haldane model represents the minimal lattice-based realization of a Chern insulator, exhibiting a quantized Hall conductance in the absence of Landau levels. Despite its conceptual elegance, the implementation in crystalline solids of the requisite pattern of Peierls phases breaking time-reversal symmetry remains experimentally demanding. In this work, we theoretically investigate the possibility to simulate the Haldane model in ultra-clean GaAs/AlGaAs heterostructures. Our proposal relies on recent experiments in which a high-mobility two-dimensional electron gas is subject to a gate-defined honeycomb electrostatic potential and a laterally periodic magnetic field generated by patterned ferromagnetic structures. The combined electrostatic and magnetic superlattices furnish a viable route to emulate the topological properties of the Haldane model.
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All authors Francesco Cioni, Lorenzo Cavicchi, Fabio Taddei, Marco Polini

Cosmology and Nongalactic Astrophysics

Exploring the Cosmic Dawn through the 21 cm Forest and High-redshift Radio Sources with the SKA

Junsong Cang, Benedetta Ciardi, Barun Maity et al. (+12 more)

The 21~cm forest, seen as absorption features in the spectra of distant radio sources, is produced by intervening neutral hydrogen and offers a direct probe of the neutral intergalactic medium during the epoch of reionization (EoR). Because it is sensitive to small-scale structure and gas temperature, it can constrain the thermal history of the early Universe and physics that affects structure formation. Detecting individual absorption lines is challenging, mainly because of their weakness and the scarcity of high-redshift radio-bright sources. Recent progress, however, has made 21~cm forest studies increasingly feasible: new statistical observables can improve sensitivity within realistic observing times, updated radio-source counts have revised expectations for suitable background quasars, and deep-learning methods can extract physical information more efficiently. In addition, new approaches have been developed to separate astrophysical effects from early galaxies from fundamental-physics effects on small-scale structure. With the Square Kilometre Array (SKA), the 21~cm forest will therefore provide a promising route to study early heating, possible exotic energy injection, dark matter properties, neutrino mass, the running spectral index, and baryon–dark-matter relative velocity. This chapter reviews recent developments in 21~cm forest research and discusses observational strategies and prospects for constraining the first galaxies and fundamental physics with SKA-Low.
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All authors Junsong Cang, Benedetta Ciardi, Barun Maity, Atsushi J. Nishizawa, Qi Niu, Yue Shao, Abinash Kumar Shaw, Hayato Shimabukuro, Tomáš Šoltinský, Tian-Yang Sun, Tsutomu T. Takeuchi, Yidong Xu, Kohji Yoshikawa, Bin Yue, Xin Zhang

Mesoscale and Nanoscale Physics

AC Conductance in n-InSb Structures with Quantum Well. Acoustic Studies

I. L. Drichko, I. Yu. Smirnov, Yu. M. Galperin et al. (+1 more)

We studied the ac conductance of an $n$-InSb quantum well structure using acoustic methods in magnetic fields up to 18 T and at temperatures ranging from 20 to 500 mK. We attribute the unusual magnetic field dependences of surface acoustic wave (SAW) attenuation and velocity observed in the experiment to the presence of a conducting layer parallel to the quantum well in the sample. We successfully separated the contributions from both the quantum well and the shunting layer, enabling the identification of their distinct conduction mechanisms. Furthermore, by employing the coincidence technique, we determined the electron g-factor in the quantum well and investigated its dependence on the degree of spin polarization.
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All authors I. L. Drichko, I. Yu. Smirnov, Yu. M. Galperin, A. V. Suslov

Mathematical Physics

A symmetry reduction of the Painlevé IV hierarchy to the Flaschka-Newell Painlevé II hierarchy

Mohamad Alameddine and Olivier Marchal

We study the isomonodromic deformation problem associated with rank-two meromorphic connections on the Riemann sphere having one regular singularity and one irregular singularity of even order at infinity, corresponding to the even Painlevé IV hierarchy. We show that the symmetry $\Psi(-\lambda)= \sigma_1 \Psi(\lambda) \sigma_1$ defines an invariant submanifold whose induced isomonodromic dynamics coincides with the Flaschka-Newell Painlevé II hierarchy. Under this identification, the corresponding Lax matrices, Darboux coordinates and Hamiltonian structures can be matched explicitly. In particular, the Hamiltonians of the first members of the Flaschka-Newell hierarchy are recovered from the even Painlevé IV hierarchy. This provides a geometric interpretation of the Flaschka-Newell hierarchy as a symmetry reduction of an isomonodromic deformation problem, complementing its classical description as a similarity reduction of the modified Korteweg-de Vries hierarchy.
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Biological Physics · Cross-listed from q-bio.QM

Extended pseudo-spectral physics-informed neural networks for phase-field models

Callum Marsh, Radek Erban and Andreas Munch

Phase-field models play a central role in the continuum description of phase separation, in which the bulk free-energy density and the interfacial thickness parameter determine pattern formation and microstructural evolution. In practice, these constitutive quantities are rarely known a priori and must be inferred from limited dynamical observations. In this work, an extended pseudo-spectral physics-informed neural network (ESPINN) framework is developed for the inverse identification of phase-field models from transient snapshot data. It enables the simultaneous recovery of both the bulk chemical potential and unknown gradient coefficients. Numerical experiments on the one-dimensional Cahn-Hilliard equation demonstrate accurate and statistically stable reconstruction in the noiseless regime, with substantial constitutive information recoverable from even a single snapshot pair. In the presence of noise, reconstruction accuracy degrades gracefully, and increasing the number of snapshots improves robustness by reducing variance across runs. These results establish ESPINN as a data-efficient and physically consistent approach for learning free-energy structure in continuum models of phase separation.
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Quantum Physics

Preparing multi-qudit states in a definite-weight subspace

Nabi Zare Harofteh and Rafael I. Nepomechie

We formulate a deterministic algorithm for preparing arbitrary multi-qudit states in a definite-weight subspace. By ordering the corresponding computational basis states according to a Gray code for multiset permutations, the state-preparation task is reduced to performing a sequence of controlled 2-qudit Gray rotations. We use this algorithm to prepare exact eigenstates of the SU(3)-invariant Heisenberg Hamiltonian, whose Bethe ansatz is nested. In particular, we describe the preparation of the Bethe states, which are SU(3) highest-weight states, as well as their lower-weight descendants. We also consider the preparation of SU(d) Dicke states and their q-deformations.
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Optics

Bode-Fano Limits to Broadband Absorption by Small Particles

Emanuele Corsaro, Andrea Alù and Carlo Forestiere

Nanostructures can be designed to absorb light efficiently at resonance despite their subwavelength footprint, but causality and passivity fundamentally limit the bandwidth over which strong absorption can be maintained. Here we derive fundamental absorption-bandwidth limits for passive, causal, linear, and temporally dispersive subwavelength objects by rigorously casting electromagnetic scattering as an equivalent impedance-matching problem. This mapping yields ultimate Bode-Fano-type constraints for optical absorption and provides rational synthesis guidelines for the material dispersion of passive nanoparticles that can approach the bounds. Our results clarify the ultimate limits for broadband light harvesting and dissipation, with implications for solar-energy conversion, photothermal hyperthermia, thermal management, and related nanophotonic technologies.
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Soft Condensed Matter

Limited surface mobility inhibits stable glass formation for 2-ethyl-1-hexanol

M. Tylinski, M. S. Beasley, Y. Z. Chua et al. (+2 more)

Previous work has shown that vapor-deposition can prepare organic glasses with extremely high kinetic stabilities and other properties that would be expected from liquid-cooled glasses only after aging for thousands of years or more. However, recent reports have shown that some molecules form vapor-deposited glasses with only limited kinetic stability when prepared using conditions expected to yield a stable glass. In this work, we vapor deposit glasses of 2-ethyl-1-hexanol over a wide range of deposition rates and test several hypotheses for why this molecule does not form highly stable glasses under normal deposition conditions. The kinetic stability of 2-ethyl-1-hexanol glasses is found to be highly dependent on the deposition rate. For deposition at Tsubstrate = 0.90 Tg, the kinetic stability increases by 3 orders of magnitude (as measured by isothermal transformation times) when the deposition rate is decreased from 0.2 nm/s to 0.005 nm/s. We also find that, for the same preparation time, a vapor-deposited glass has much more kinetic stability than an aged liquid-cooled glass. Our results support the hypothesis that the formation of highly stable 2-ethyl-1-hexanol glasses is inhibited by limited surface mobility. We compare our deposition rate experiments to similar ones performed with ethylcyclohexane (which readily forms glasses of high kinetic stability); we estimate that the surface mobility of 2-ethyl-1-hexanol is more than 4 orders of magnitude less than that of ethylcyclohexane at 0.85 Tg.
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All authors M. Tylinski, M. S. Beasley, Y. Z. Chua, C. Schick, M. D. Ediger

Chemical Physics

The Finite Coulomb Lattice Sum: A Resolution of Conditional Convergence through Exact Shape and Size

Yang He and Zhonghan Hu

This work examines conditionally convergent Coulomb lattice sums under periodic boundary conditions. The recently developed finite lattice sum cleanly decomposes the series into three distinct components: a periodic bulk term $\nu_{\rm pbc}$, a shape-dependent non-periodic boundary term $\nu_{\rm b}$, and a finite-size correction term $\nu_{\rm corr}$. This rigorous formulation explicitly parameterizes the geometry of a finite lattice by its exact shape and size and takes an effective pairwise form. We analyze it in detail and compare it with various derivations of lattice sums in the literature. Perspectives on future applications are discussed, including analytical developments for arbitrarily shaped crystals and numerical mesh-type algorithms for condensed matter simulations.
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Cosmology and Nongalactic Astrophysics

Measuring local primordial non-Gaussianity from the clustering of DESI DR1 LRGs and QSOs

Z. Brown, B. Levi, H. Randall et al. (+42 more)

We report the first measurement of primordial non-Gaussianity (PNG), parameterized by $f_{\mathrm{NL}}$, in the configuration space two-point correlation function (2pcf). We employ simulation based modeling and a novel approach for the mitigation of imaging systematics. We apply this method to samples of luminous red galaxies (LRG) and quasars (QSO) observed by the Dark Energy Spectroscopic Instrument (DESI) during the first year of its observations (DR1). The observed 68% CL interval on $f_{\mathrm{NL}}$ is $-3^{+22}_{-21}$ using LRGs, and $ 0^{+17}_{-16}$ using QSOs. The joint measurement yields $f_{\mathrm{NL}} = -3^{+12}_{-12}$ at $\ [68\%]$ CL. Our pipeline imposes a Gaussian prior on the value of $p$ (which defines the PNG bias via the Universality relation), with $p_{\rm LRG} = 1.0 \pm 0.1$ and $p_{\rm QSO} = 1.6\pm 0.1$. The observed constraining power of DESI tracers significantly exceeds that of previous large-scale structure (LSS) surveys, and encouragingly, approaches the sensitivity of CMB probes of PNG.
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All authors Z. Brown, B. Levi, H. Randall, E. Chaussidon, R. Demina, A. G. Adame, S. Avila, V. Gonzalez-Perez, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, Biprateep Dey, P. Doel, J. E. Forero-Romero, E. Gaztanaga, Satya Gontcho A Gontcho, G. Gutierrez, C. Hahn, K. Honscheid, D. Huterer, M. Ishak, R. Joyce, D. Kirkby, C. Lamman, M. Landriau, M. Manera, A. Meisner, R. Miquel, S. Nadathur, W. J. Percival, I. Perez-Rafols, A. Ross, G. Rossi, L. Samushia, E. Sanchez, M. Schubnell, J. Silber, D. Sprayberry, G. Tarle, B. A. Weaver, H. Zou

Quantum Physics

Reachability and optimal-time certificates for quantum control

Younes Naceur and Llorenç Balada Gaggioli

Finite-time control is central to quantum technologies, yet rigorous limits on reachable targets and optimal control times remain largely unknown. We develop a framework for finite-time reachability and optimal-time certificates in constrained quantum control based on moment relaxations with implicitly time-dependent differential constraints. For fixed control horizons and control constraints, the method yields rigorous upper bounds on achievable terminal fidelities, lower bounds on the optimal control times required to reach them, and certificate gaps for benchmarking explicit control pulses. We demonstrate the versatility of our framework in three use cases: entangled-state preparation in two and three qubits, one-qubit gate synthesis across different control geometries, and excitation transfer in an $N$-qubit $XX$ chain. Our work establishes differential moment hierarchies as a practical tool for certifying reachability limits and optimal control times in quantum control, providing hardware-aware quantum speed limits while highlighting structure exploitation as a key ingredient for scalable certification.
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Optics

The Quantum Split-Step Fourier Algorithm for Nonlinear Optical Waveguides

Fabio Biancalana

We introduce the Quantum Split-Step Fourier (QSSF) algorithm for nonlinear optical waveguides, a numerical framework that combines split-step propagation of the nonlinear Schrödinger equation with a commutator-preserving Bogoliubov evolution of Gaussian quantum fluctuations. The method propagates the classical mean field together with the Bogoliubov matrices $U$ and $V$, from which reduced second moments, covariance matrices, symplectic eigenvalues, and entropic measures are constructed for arbitrary spectral windows. Applied to soliton-driven resonant radiation, QSSF shows that the selected radiation band acquires a steadily increasing von Neumann entropy and a corresponding loss of purity, quantifying its entanglement with the rest of the spectrum in the lossless Gaussian setting. The analysis also reveals a surprisingly pronounced low-dimensional structure: although the radiation occupies many Fourier bins, its reduced Gaussian state is dominated by only a few Williamson modes. QSSF therefore provides a practical information-theoretic diagnostic for quantum correlations in nonlinear frequency conversion, supercontinuum generation, and multimode squeezed-light formation in ultrafast waveguide platforms.
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